James E. Moore, Ph.D. - Texas A&M University - Bioengineering Seminar Series - March 30, 2010, 11:00 AM - 12:00 PM, IBB Suddath Rm. 1128

Abstract:

While stents have revolutionized the treatment of atherosclerosis, they still suffer clinical failures due to restenosis. We have analyzed the biomechanical interaction of stents with the artery wall from both the fluid mechanics and solid mechanics points of view. These studies incorporate a variety of approaches, including computational modeling and in vitro experimentation. These studies indicate that there are certain design features that contribute to a potentially bad biomechanical environment, which in turn leads to additional intimal hyperplasia and eventually restenosis. Our results indicate that inclusion of biodegradable features in stents can minimize some of these deleterious effects. The concept of biodegradable stents dates back at least to 1990, yet no designs are approved for the US market. This is in part due to the challenges associated with designing a structure that provides an appropriate amount of support to the artery wall for a sufficient period. Material models for the polymers typically used in medical applications are insufficient for this design challenge. We have developed a new class of material models that accounts for the effects of cyclic strain in accelerating degradation. These models were implemented in a finite element modeling package and applied to representative stent designs. The results indicate that some parts of the stent degrade faster than others, depending on the stent design. Non-uniform biodegradation could lead to dangerous embolous development from non-degraded pieces breaking off of the main structure. This new class of material models, if coupled with appropriate experimental data on material behavior under cyclic loading, provides the opportunity to predict where and when a biodegradable stent begins to lose structural integrity. It should also be possible to design stents for more uniform degradation profiles.

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